1. Field of the Invention
Catalytically active compositions for use in plating metal on a nonconductive substrate.
2. Description of the Prior Art
U.S. Pat. No. 3,011,920 (Shipley) describes a process in which a colloidal solution is prepared by mixing an aqueous acid solution of palladium chloride with an aqueous acid solution of stannous chloride and optionally including a tin salt such as sodium stannate. This is purported to produce a lyophilic colloid which, after acceleration with an acid or alkaline solution such as hydrochloric acid or sodium hydroxide, provides a sensitizing layer for the subsequent electroless plating of a metal such as copper.
U.S. Pat. No. 3,672,923 (Zeblisky) describes solid compositions dilutable to optically clear sensitizing solutions for electroless plating. These solutions are prepared by combining a dilute solution of a noble metal salt in hydrochloric acid with a hydrochloric acid solution of a stannous salt such as stannous chloride dihydrate. The mixture is heated and then subsequently cooled and evaporated to dryness under vacuum to constant weight. The solid composition, as described, may then be reconstituted in hydrochloric acid to provide an active sensitizing solution.
U.S. Pat. No. 3,904,792 (Gulla et al) describes a catalyst containing an acid soluble salt of a catalytic metal, a stannous salt, an acid and an extraneous source of halide ions.
U.S. Pat. No. 3,627,558 (Roger et al) describes the use of chelating agents such as disodium EDTA for pretreatment of the substrate where metal oxides may be present.
U.S. Pat. No. 3,874,897 (Fadgen et al) describes a Lewis base modified palladium-tin catalyst.
U.S. Pat. No. 3,274,022 (Rhoda) describes the use of EDTA as a stabilizer for palladium containing catalysts. This reference, however, does not relate to palladium tin catalysts of the type to which the present invention is concerned.